100 STRATIGRAPHICAL GEOLOGY 



north-west, till only the Upper Cambrian is represented. On 

 this view the correlation would be as follows, and the great 

 difference in thickness more easily accounted for : 



Southern area. Northern area. 



'Green and purple slates. Green and purple slates \QQQ f ee f 



Felspathic sandstones and lavas. Purple sandstones, etc. / 



Purple slates. 



Purple sandstones. 

 ^ Basal conglomerate. 



In Normandy a somewhat different facies of the Cambrian is 

 found, inasmuch as it includes an important limestone formation 

 which is largely quarried for marble. Near Caen, May, and Clecy 

 the succession is : 



Feet. 

 Green slates and limestone, without fossils . . . . . 130 



Massive limestones (red and grey marbles) ..... 250 



Red slates and red marble ........ 20 



Purple sandstone and conglomerate ...... 200 



600 



All these beds thicken southward till, near Montbard and 

 Fourneaux, they have a combined thickness of nearly 2000 feet, 

 while the overlying felspathic sandstones thin out entirely, and 

 finally, south of St. Lo, the whole series disappears beneath an 

 overstep of the Gr&s armoricain (Arenig) on to the Archaean rocks, 

 and the Cambrian only comes in again to the south of Ernee and 

 Mayenne. 



2. Iberian Peninsula 



Cambrian rocks occur in several parts of Spain and Portugal, 

 in Asturias and Galicia, in Leon, in Seville near Ciudad-Real, and 

 near Busaco in Portugal ; the Paradoxides fauna having been found 

 in several of these districts. The area which has been most 

 completely explored and described is that of Asturias and Galicia 

 in the north-west, and in 1882 Dr. Barrois referred the following 

 groups to the Cambrian : 26 



T -IT ( Greenish sandy shales with beds of green sandstone 100 to 

 La Vega I 3Q() feet 



Beds | Limestones and shales 60 to 200 feet. 

 Rivadeo /Green quartzites and slates. 



Beds \Green slates and bluish phyllites. 



The upper group yielded species of Paradoxides, Conocoryphe, 

 Arionellus, and Trochocystites bohemicus, so that it is clearly of 

 Middle Cambrian age. It is overlain by conglomerates and sand- 

 stones with Bilobites which are comparable with the Gres /els- 



